Removing low frequency rumble with omnidirectional microphones

This happened by accident.


2 Beyer M55 were connected in series before feeding the preamplifier input.


They happened to be out of phase.


This canceled low frequencies from far sources. Explanation seems to be the large wavelength of low frequencies.


Also most of the ugly bass reverberation of a room disappeared.


Note:(Is it correct assuming that outdoor sounds from very far would be almost completely canceled as the arrive practically at the same time to both mics. So when recording direct to mono or stereo with microphone arrays a good trick may be to arrange some of the mics to be out of phase. It should be easily done while physically connecting the cable outputs of microphones together in parallel series combinations as described on the following euroelectron posts).


And while close micing with them each source had full natural body.


This trick may prove useful in direct recording to mono or stereo using many microphones, their outputs connected in series-parallel combinations.


Signal path:


M55 in series with (-M55) - Canford input step up transformer - Pleiades V4, 3.4V battery - Realistic disco mixer at mono mic in - Sennheiser HD580


More on this Pleiades connection on the following euroelectron posts.